AB0542 ANTIPHOSPHOLIPID ANTIBODY CARRIERS WITH THROMBOCYTOPENIA COULD BE AN INDEPENDENT PHENOTYPE OF PRIMARY ANTIPHOSPHOLIPID SYNDROME
Authors: Y. Shi, J. Zhao, X. Zeng
Journal: Annals of the Rheumatic Diseases (2022)

Background Among patients with immune thrombocytopenic (ITP), 10-20% of them were found with positive antiphospholipid antibodies (aPLs) but without typical clinical manifestations of antiphospholipid syndrome (APS), especially thrombotic events 1 . Objectives To compare the clinical characteristics and prognosis between aPLs carriers and patients with APS. Methods This is a single center prospective cohort study consecutively enrolling thrombocytopenic patients with continuous positive aPLs. Patients developing thrombotic events are classified as the APS group. The exclusion criteria are other underlying connective tissue diseases such as lupus and other causes that might manifest as thrombocytopenia, such as virus infection, hypersplenism, etc. Results This cohort included 47 thrombocytopenic patients with continuous positive aPLs and 55 with diagnosed primary APS. The proportion of thrombotic high risk demographic characteristics including smoking, hypertension, and higher level of homocysteine are higher in the APS group (p = 0.03, 0.04, 0.03, respectively). The prevalence of nephropathy was significantly higher in patients with diagnosed APS [0 vs 7 (12.7%), p =0.01]. Laboratory results and antibody profiles are presented in Table 1. The platelet count of aPLs carriers at admission was lower than APS patients [26×10 9 /L (9×10 9 /L, 46×10 9 /L) vs 64×10 9 /L (24×10 9 /L, 89×10 9 /L), p = 0.0002]. The proportion of positive anti-β2-glycoprotein I, anticardiolipin and lupus anticoagulant separately was similar, but triple aPLs positivity is more common in primary APS patients with thrombocytopenia [24 (51.1%) vs 40 (72.7%), p = 0.04]. There is no significant differences over the complement levels between the two groups [p = 0.2 for low complement 3 (C3), p = 0.8 for low C4]. Regarding the treatment response, the complete response (CR) rate is similar between aPLs carriers and primary APS patients with thrombocytopenia (p = 0.2). Nonetheless, the proportion of response, no response and relapse differed significantly between the two groups [13 (27.7%) vs 4 (7.3%), p &lt; 0.0001; 5 (10.6%) vs 8 (14.5%), p &lt; 0.0001; 5 (10.6%) vs 8 (14.5%), p &lt; 0.0001, respectively]. In Kaplan-Meier analysis (Figure 1), primary APS patients had significantly more thrombotic events than aPLs carriers (p = 0.0006). aPLs carriers with thrombocytopenia share similar clinical manifestations with primary APS patients but hardly develop thrombotic events. Figure 1. Kaplan-Meier analysis of thrombotic events. aPLs: antiphospholipid antibodies; PAPS: primary antiphospholipid syndrome. Table 1. Baseline characteristics of laboratory results and antibody profiles. Characteristics aPLs carriers (n=47) Primary APS with thrombocytopenia (n=55) p-value Laboratory results, median (Q1, Q3) Platelet count (×10 9 /L) 26 (9,46) 64 (24, 89) 0.0002* hsCRP (mg/L) 1.39 (0.475, 2.845) 1.08(0.41, 2.565) 0.8 ESR (mm/h) 5.5 (2.75, 10.75) 7.5 (5, 14.25) 0.06 LDH (U/L) 221 (176, 252) 228 (184.8, 282) 0.3 Low C3, n (%) 3 (6.4) 9 (16.4) 0.2 Low C4, n (%) 5 (10.6) 8 (14.5) 0.8 Antibody profiles, n (%) Positive aCL 45 (95.7) 33 (69.1) 0.3 Positive Anti-β2GP I 38 (80.9) 48 (87.3) 0.5 Positive LA 35 (74.5) 50 (90.9) 0.05 Triple positivity 24 (51.1) 40 (72.7) 0.04* Positive Coombs, 6 (12.8) 10 (18.2) 0.4 *p &lt; 0.05, statistically significant. aPLs: antiphospholipid antibodies; APS: antisphopholipid syndrome; Q1/3: quantile 1/3; hsCRP: hypersensitive C-reactive protein; ESR: erythrocyte sedimentation rate; LDH: lactate dehydrogenase; C3/4: complement 3/4; aCL: anticardiolipin; GP: glycoprotein; LA: lupus anticoagulant. Conclusion In the absence of other high risk factor for thrombosis, Thrombocytopenia could be an independent and long-lasting clinical phenotype for aPLs carriers. References [1]Bidot CJ, Jy W, Horstman LL, Ahn ER, Yaniz M, Ahn YS. Antiphospholipid antibodies (APLA) in immune thrombocytopenic purpura (ITP) and antiphospholipid syndrome (APS). Am J Hematol . Jun 2006;81(6):391-6. Disclosure of Interests None declared